Frost dates by ZIP code: The nearest NOAA stations to your ZIP, 1991-2020 normals
Enter a five-digit ZIP code. PlainClimate finds its center (Census Bureau 2024) and the five nearest NOAA stations with frost dates, and shows each station's last spring and first autumn 32°F dates with its distance and elevation.
Frost dates near ZIP 20721
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 20721 in zone 7b (the coldest night of a typical year: 5 to 10°F).
The nearest station, Glenn Dale, MD, is 4 miles from the ZIP's center: its last spring frost comes after April 22 in half of years and after May 9 in one year in ten.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Glenn Dale, MDGlenn Dale Bell Station | 4 mi | 150 ft | April 22 | May 9 | October 22 | – |
| Upper Marlboro, MD3 mi NNW | 4 mi | 130 ft | April 9 | April 24 | October 29 | 7b |
| National Arboretum DC, MD | 10 mi | 50 ft | March 29 | April 11 | November 8 | 8a |
| Beltsville, MD | 11 mi | 145 ft | April 10 | May 1 | November 1 | 7b |
| Laurel, MD3 mi W | 13 mi | 400 ft | April 5 | April 19 | November 9 | 7b |
Frost comes later in spring at higher and colder stations and earlier in low, open ground: prefer a station at a similar elevation to yours. Hardiness zone in the table: the USDA's rule (the average of each year's coldest night, 1991-2020) applied to the station's own record.
Every frost threshold at Glenn Dale
NOAA publishes the dates for several temperatures and odds. A 30% spring date means a 3-in-10 chance of a later frost (the convention almanacs use); 50% is the median; 10% the cautious date.
| Threshold | Spring, 10% | Spring, 30% | Spring, 50% | Spring, 90% | Autumn, 50% | Autumn, 10% |
|---|---|---|---|---|---|---|
| 36°F (light frost) | May 20 | May 10 | May 3 | April 18 | October 12 | September 30 |
| 32°F | May 9 | April 29 | April 22 | April 3 | October 22 | October 7 |
| 28°F (hard freeze) | April 30 | April 15 | April 7 | March 23 | November 1 | October 16 |
| 24°F | April 13 | April 2 | March 26 | March 10 | November 11 | October 29 |
Source: NOAA NCEI 1991-2020 annual normals; ZIP centers: Census Bureau 2024 Gazetteer; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. Autumn 10%: one year in ten has its first frost before this date.